Probability

Each of the numbers 1 through 10 inclusive has been written on a separate piece of paper. The 10 pieces of paper have been placed in a hat. If one piece of paper is selected at random, with replacement, find the probability that the number selected is:

a. greater than 3
b. even
c. odd or greater than 3
d. odd or less than 9

Solution Preview

Well, first consider that because we are allowed to return the selected pieces of paper in the hat, then for each of these experiments the all possibilities is C(10,1)=10 which will be the denominator of the probability as you will see.

a) Ok, how many numbers are greater than 3 in the numbers from 1 to 10? They are actually all the numbers from 4 to 10. Therefore we have 7 options. C(7,1)=7. Then P=7/10.

b) How many even numbers are there between 1 and 10 (inclusive)? We have (2,4,6,8,10). Therefore there are 5. And we have ...